In any instructional situation, there will almost always be something students “bring to the table” in the form of prior knowledge, Getting students to remember, and activate the useful parts of that prior knowledge can help them engage mental resources that will help them understand new material. When students learn things in a void without engaging this prior understanding, they frequently don't integrate what the knew with what they are learning. This can leave student knowledge in a form that cognitive scientists sometimes refer as “inert”. Engaging prior knowledge can help student connect what they know and help them be ready for new learning. Questions that engage prior knowledge also serve the purpose of formative assessment, by letting the instructor know what students already know, and therefor the approprite point from which the instruction should begin.

Instructors should be aware that questions engaging prior knowledge can result in an instructor needing to think on their feet and alter instructional plans. Often students are thinking about things in ways that are different than the instructor originally envisioned.

An example from our instruction was at the start of quantum mechanics the instructor told students to use their small whiteboards and “Write down the formula for the electric potential due to a point charge”. This is a formula which all students had seen in one form or another several times. Many had even seen the formula in their high school physics classes. Having students actively remember this formula helped students be ready for the upcoming class discussion about potentials. Furthermore, because several students made errors, such as using 1/r2, and this could be brought to the students attention so that they were aware that they could not use the field and potential formulas interchangably. There were also students who used the constant “k” and others who used 1/4(pi)(epsilon-naught). Several students saw lights go on when they realized that these were two different ways of writing the same constant.

In the few cases of students who had completely forgotten the formula, this allowed them to quickly “get up to speed” at the start of class instead of being lost. It also cued them into the idea that this was something they were expected to know by heart.

Whiteboard questions that consistently result in all students quickly getting fully correct answers are “aimed too low”. The questions are more effective if they require students to do several seconds (or more) of active thinking in order to produce an answer. On the other extreme, if very few students produce a viable answer, the question has become almost entirely a form of formative assessment, that allows the instructor to realize that some “backfill” or other adjustment to instruction is needed before proceding.